Starting induction motors



,I; BRUNCKE N.. STARTING'INDUICTION MOTORS. APPLICATIION FILED DEC 2, I320.

1,537,886.- 'Pa tenfed flee. 5-, 1922.

i iatented Dec. 5, 1922.

UNITED STATES.

PATENT OFFICE.

JOHANNES BRUNCKEN, OF COLN-BICKENDOBF, GERMANY.

STARTING IN DUCTION MOTORS.

Original application filed June 13,1920, Serial No. 351,240. Divided and this application filed December 2, 1920. Serial No. 427,834.

To all whom it may concern:

Be it known that I, J OHANNES BRUNCKEN, citizen of Germany, residing at Coln-Bickendorf, Germany, have invented certain new and useful Improvements in Starting Induction Motors (for which I have obtained patents in Great Britain, No. 140,745, April i, 1921, and in France, No. 507,394, June 21, 1920), of which the following is a specification, reference being had therein to the accompanying drawing.

This invention relates to certain new and useful improvements in motors, being an improvement and development of the double induction motor described in application No. 351,240, filed Jan. 13, 1920, and is a division thereof. That motor comprises two stators co-operating with two armatures upon a common shaft, these carrying a squirrel cage winding, the bars of which extend throughout the length of both armatures and are united at the ends by short circuiting connections, and in the middle by a ring of high specific resistance.

In an arrangement of this kind described by Boucherot & Cie in German Patent No. 108543, the resistance of the centre ring amounts to fifteen or twenty times the internal resistance of the motor. Thus theresistance is relatively high and the conductors of which it is formed may easily suffer damage since they have to be long and thin. Within them the energy taken by the motor during starting has to be converted into heat, and that, taken in conjunction with the considerable mechanical stresses to which the resistance is subjected, further diminishesthe durability of the construction. But a motor started. in the manner described in my application. No. 351,240 can be constructed. with resistances in its rotor of much smaller ohmic value by making the connection between the rotors with a resistance of the same order as that of the squirrel cage winding. According to this invention, therefore, these resistances are constructed in the form of binder wires surrounding the armature bars where they pass through the air between the two armature cores.

The method by which the motor is started makes it possible to dispense with the high resistance connection between the rotors. By this method the two stator windings are successively connected in series in star, one

in star in series with the other joined in mesh, both in series in mesh, both in parallel in star, and finally both in parallel in star, the field of one of the windings being shifted through 180 with respect to the field of the other winding. The rotor arrangement is illustrated in cross section in the accompanying drawing.

1 are the armature bars, the end portions of which lie in slots or tunnels in the armature core in a well known way, while the middle portions, as shown, extend freely through the air between the two armatures. w are the binder resistance wires, each of which is connected with each of the bars. The ohmic resistance of these binders may be approximately equal to the internal resistance of the armature itself. Consequently, not so large a proportion of the energy absorbed in starting is dissipated in the binders. Moreover, the binders form a stout and a durable resistance, since the conductive element between successive rods can be short and of comparatively large cross section. The possibility of this results from the method of starting, for on account of the small flux existing at first the rotor currents have a value several times the normal value and the internal rotor E. M. F. is correspondingly small, and the fact that the series connection of the two stator windings correspondingly diminishes the E. M. F. applied to the separate stator phases. Consequently, the E. M. F. induced in the rotor is correspondingly less, and in order that the motor may still exert the full torque, the rotor currents must be correspondingly inreased; for the rotor torque is the product of the flux and the rotor current. If the flux is lessened through the stator, the E. M. F. being less, the rotor current must be come spondingly increased, so that the product of the flux and current remains the same.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be performed, I declare that what I claim is 1. In a motor of the type described, a middle connector and armature bars, the middle connector constructed as a set of binders holding the armature bars together and connected with each bar, each binder being of such cross section that the ohmic value of the resistance is small and of the same order as the internal resistance of the armature. the internal resistance of the armature it 10 2. In a motor of the type described, armaself.

ture cores mounted on the same shaft, arma- V Intestimony whereof I afiix my signature ture bars the end portions of which lie in in the presence of two Witnesses.

slots in said core, the intermediate portions of said bars extending freely through space, JOHANNES BRUNCKEN' and binder Wires each of which is connected Witnesses: v With each of said bars, the ohmic resistance AUG; BAUER,

of said binders being substantially equal to ZEM BLUNEM. 

